A typical hammer-type stapler includes a handle for enabling an operator to manually grasp the stapler and a frame which is fixed to or forms a part of the handle. The frame carries the usual staple driving components which include a structure defining a drive track, a staple driving element movable through the drive track and a magazine assembly for guiding a staple stick in the magazine assembly into the drive track so that successive leading staples are driven by the staple driving element through the drive track into the workpiece during the drive stroke of the staple driving element and for biasing a leading staple to move into the drive track during the return stroke of the staple driving element.
Staplers of the hammer-type which are known fall generally into two categories. Probably the most prevalent is the hammer-type stapler in which the staple driving element is fixed to the frame and handle. In this category, the magazine and staple drive track structure are moved with respect to the driver on impact. Examples of hammer-type staplers of the fixed driver-movable magazine category are exemplified in U.S. Pat. Nos. 2,664,565 and 2,667,639. In the other category, the magazine assembly and the drive track structure are fixed with respect to the frame and handle and the staple driving element is moved through the drive track in response to the impact. Examples of hammer-type staplers of this type are illustrated in U.S. Pat. Nos. 2,325,341 and 2,896,210.
Despite the fact that both fixed driver and fixed magazine hammer-type staplers have been known for decades, there always exists a need to improve the operation and efficiency of known devices.
One characteristic of prior art hammer-type staplers is that there is a tight workpiece clearance condition with respect to the hand of the user engaging the workpiece surface during the hammering operation. This is particularly true when the workpiece is a fairly extensive planar surface such as a floor or a roof where staplers of the hammer-type are often used. Two key factors contribute to this hand clearance problem. First, the impacting surface of the stapler provided by the drive track defining structure of the stapler cannot be simply made longer without increasing the distance of the drive stroke. Lengthening the drive stroke also lengthens the distance the staple must be moved in order to be driven into the workpiece. In general, it can be stated that increasing the distance the staple must be moved in order to be driven increases the likelihood of jams and the difficulties in accommodating a wide range of staple sizes in the same magazine assembly. The capacity of the magazine assembly provides the other limiting factor. The stick feed track defining structure of the magazine assembly which is rigidly secured to the drive track structure must extend rearwardly within the handle in order to accommodate two staple sticks, thus rendering it impractical to simply position the handle where it would be most desirable from a hand clearance viewpoint.
In practice, it is often the case that a staple will be driven into the workpiece at an angle rather than perpendicularly because the operator simply does not want his knuckles to come too close to the workpiece surface. In many installations, it can be important that the crown of the staple be flush with respect to the workpiece surface, as by a perpendicular drive, rather than somewhat cocked with respect to the workpiece surface, as can be the case when the staple is driven in at an angle. There is a need to alleviate the problem of knuckle clearance so as to more readily ensure that each staple will be driven flush to the workpiece surface.